The ancient eyes, each just 1.25mm across, belonged to a tiny crane-fly that lived 54 million years ago. Discovered by Lund University researchers, evidence of pigment within them is shedding new light on the evolution of compound eyes.

Eumelanin — a natural pigment found for instance in human eyes — has, for the first time, been identified in the fossilized compound eyes of 54-million-year-old crane-flies. It was previously assumed that melanic screening pigments did not exist in arthropods.

“We were surprised by what we found because we were not looking for, or expecting it,” says Johan Lindgren, an Associate Professor at the Department of Geology, Lund University, and lead author of the study published this week in the journal Nature.

The researchers went on to examine the eyes of living crane-flies, and found additional evidence for eumelanin in the modern species as well.

By comparing the fossilized eyes with optic tissues from living crane-flies, the researchers were able to look closer at how the fossilization process has affected the conservation of compound eyes across geological time.

The fossilized eyes further possessed calcified ommatidial lenses, and Johan Lindgren believes that this mineral has replaced the original chitinous material.

This, in turn, led the researchers to conclude that another widely held hypothesis may need to be reconsidered. Previous research has suggested that trilobites — an exceedingly well-known group of extinct seagoing arthropods — had mineralized lenses in life.

“The general view has been that trilobites had lenses made from single calcium carbonate crystals. However, they were probably much more similar to modern arthropods in that their eyes were primarily organic,” says Johan Lindgren.

Compound eyes are found in arthropods, such as insects and crustaceans, and are the most common visual organ seen in the animal kingdom. They are made up of multiple tiny and light-sensitive ommatidia, and the perceived image is a combination of inputs from these individual units.

An ancient relative of today’s rollers with a deep blue hue adds to our understanding of nature’s prehistoric palette.

SOMEWHERE OVER THE rainbow 48 million years ago, a happy little blue bird flew—until it soared over a lake belching toxic gases and died. The lake’s sediments then entombed the bird’s body, exquisitely preserving the oldest fossil evidence of blue feathers ever found.

Researchers could infer E. brachyptera’s blue color only because they could compare it with its modern relatives, the rollers. Tiny structures preserved in the fossilized feathers resemble those that give modern birds either blue or gray hues, depending on their arrangement.

And as far as we know, blue feathers have been fairly uncommon through time: Of the 61 lineages of living birds, only 10 have species with E. brachyptera’s most probable coloration. But since modern rollers are far likelier to have blue than gray feathers, the researchers conclude that the ancient bird was a deep blue. It’s the first time that such a feather color has been reconstructed from the fossil record. “I would say that, for me, that was the most exciting and important part of this research,” says lead study author Frane Babarović, a Ph.D. student at the University of Sheffield.

This can be observed by studying the melanin packages called melanosomes, which are shaped like little cylindrical objects less than one-thousandth of a millimetre and vary in shape from sausage shapes to little meatballs.

However, besides iridescent colours, which is structural, birds also make non-iridescent structural colours.

Those are, for example, blue colour tones in parrots and kingfishers. Until now, it was not known if such colours could be discovered in fossils.

This blue structural colour is created by the dense arrangement of cavities inside feathers, which scatters the blue light. Underneath is a layer of melanin that absorbs unscattered light.

Paleontologists have shown that the feather itself, which is made of keratin, does not fossilise while the melanin does. Therefore, if a blue feather fossilised, the dark pigment may be the only surviving feature and the feather may be interpreted as black or brown.

Now researchers from the University of Bristol, led by Frane Barbarovic who is currently at the University of Sheffield, have shown that blue feather melanosomes are highly distinct from melanosomes that are from feathers expressing black, reddish-brown, brown and iridescent, but overlap significantly with some grey feather melanosomes.

By looking at plumage colourations of modern representatives of fossil specimen and reconstructing which colour was the most likely present in the fossil specimen, they were able to discriminate between melanosomes significant for grey and blue colour, leading to the reconstruction of prehistoric Eocoracias brachyptera as a predominantly blue bird.

Frane Barbarovic said: “We have discovered that melanosomes in blue feathers have a distinct range in size from most of colour categories and we can, therefore, constrain which fossils may have been blue originally.

“The overlap with grey colour may suggest some common mechanism in how melanosomes are involved in making grey colouration and how these structural blue colours are formed.

“Based on these results in our publication we have also hypothesized potential evolutionary transition between blue and grey colour.”

The research team now need to understand which birds are more likely to be blue based on their ecologies and modes of life. The blue colour is common in nature, but the ecology of this colour and its function in the life of birds is still elusive.

Frane Barbarovic added: “We also need to understand how grey colour is made. This is made in a very different way in birds than it is in mammals. We believe it is related to how the melanosome shape can result in a kind of self-assembling process in the feather and the surface tension of the melanosomes pull them into certain configurations inside a feather as it forms.”

Argentine fossils take oak and beech family history far into Southern Hemisphere

June 7, 2019

One of the world’s most important plant families has a history extending much farther south than any live or fossil specimen previously recorded, as shown by chinquapin fruit and leaf fossils unearthed in Patagonia, Argentina, according to researchers.

“The oak and beech family is recognized everywhere as one of the most important plant groups and has always been considered northern,” said Peter Wilf, professor of geosciences and associate in the Earth and Environmental Systems Institute, Penn State. “We’re adding a huge spatial dimension to the history of the Fagaceae family, and that’s exciting.” The plant family also includes chestnuts and the closely related chinquapins.

Common in the Northern Hemisphere and Asian tropics, Fagaceae cross the equator only in Southeast Asia, and even there just barely. The latest study, published today (June 7) in Science, extends the family’s biogeographical history and suggests a Gondwanan supercontinent legacy in Asian rainforests larger than previously thought.

The researchers first found fossils resembling some oak leaves, with straight secondary veins and one tooth per secondary vein, at Laguna del Hunco, Chubut province. The leaves comprise about 10 percent of the thousands of 52-million-year-old leaf fossils, representing almost 200 species, found at the site over two decades in a long-term project between Penn State, Cornell University and Museo Paleontológico Egidio Feruglio (MEF), Trelew, Argentina.

For years the researchers hesitated to classify the leaves, because paleobotanist Edward Berry had assigned similar fossils to another family, and any claim of Fagaceae at so remote a location would require much more supporting evidence.

Later, the team unearthed rare fruit fossils — two fruit clusters, one with more than 110 immature fruits — at the site and compared them to living relatives. They found that these were fossils of ancient Castanopsis, an Asian chinquapin that today dominates the biodiverse, lower elevation mountain rainforests of Southeast Asia.

“One of the first clues was a little lip where the fruit is splitting open,” Wilf said. “I recognized this lip as being similar to the fruit of the Japanese chinquapin. Then I realized there’s a nut inside.”

The nuts are fully encased in a scaly outer covering, or cupule, that splits open when the fruits mature. The cupules are arranged on a spike-like fruiting axis, and the young nuts retain delicate parts from their flowering stage. Their features are just like the living Castanopsis, Wilf said, and the fruits confirm that the leaves are Fagaceae.

“This is the first confirmed evidence that Fagaceae, considered restricted to the Northern Hemisphere, was in the Southern Hemisphere,” said Maria Gandolfo, associate professor, Cornell University. “This is remarkable and allows us to rethink the origins of the fossil flora.”

The fossils date to the early Eocene 52.2 million years ago. They are the only fossilized or living Fagaceae ever found south of the Malay Archipelago, the island chain just north of Australia.

During the globally warm early Eocene there was no polar ice, and South America, Antarctica and Australia had not completely separated, comprising the final stage of the Gondwanan supercontinent. The researchers think animals had helped disperse the chinquapin’s ancestors from North to South America at an earlier time. The plants thrived in the wet Patagonian rainforest, whose closest modern analog is the mountain rainforests of New Guinea.

“Before the current semi-desert conditions, trees covered Patagonia,” said Rubén Cúneo, director of MEF. “Changes in climatic conditions turned it into a shrubland, and the trees were displaced.”

The chinquapins may have also ranged into then-adjacent Antarctica and on to Australia, said Wilf. Castanopsis may have survived in Australia until the continent collided with Southeast Asia, where today chinquapins are keystone species, providing forest structure and food and habitat for birds, insects and mammals.

“We’re finding, in the same rocks as Castanopsis, fossils of many other plants that live with it today in New Guinea and elsewhere, including ferns, conifers and flowering plants,” said Wilf. “You can trace some of the associations with Castanopsis seen in Eocene Argentina to southern China and beyond.”

Today, Castanopsis plays an important role in intercepting year-round mountain precipitation that delivers clean water for drinking, fishing and agriculture to more than half a billion people and sustains diverse freshwater and coastal ecosystems. However, humans are clearing these rainforests for timber, development and crop cultivation, and modern climate change is increasing droughts and fire frequency.

“These plants are adaptable if given time and space,” Wilf said, adding Castanopsis’ trek from Patagonia to Southeast Asia occurred over millions of years and thousands of miles. “But the pace of change today is hundreds of times faster than in geologic time. The animals that depend on these plants are adaptable only to the extent that the plants are, and we are one of the animals that depend on this system. If we lose mountain rainforests, really fast we lose reliable water flows for agriculture, clean coral reefs offshore, biodiversity and much more.”

This study has implications for extinction in the face of climate change, according to Kevin Nixon, professor and L.H. Bailey Hortorium curator, Cornell University. He said Castanopsis went extinct in Patagonia due to a major extinction caused by the slow cooling and drying of the climate that occurred with the glaciation of Antarctica and the rise of the Andes.

“Those kinds of climate changes can have massive effects on biodiversity,” Nixon said. “The relevance of understanding this is we can start to look at extinction processes. The better we can understand what causes extinction, the better we can deal with it.”

The National Science Foundation, National Geographic Society and David and Lucile Packard Foundation funded this research.

In the Eocene Epoch, there was a reptile that had teeth equipped for biting through flesh, its hind legs were a lot longer than its front legs and instead of claws, its toes were each capped with hooves. How did this living nightmare come to evolve?

This snapshot in time reveals that fish may have coordinated their motion long ago

Fossilized fish captured mid-swim offer a rare glimpse into extinct animal behavior — and suggest that swimming in schools developed at least 50 million years ago.

A limestone shale slab from the Eocene Epoch reveals that extinct, thimble-sized fish called Erismatopterus levatus may have coordinated their motion similar to how fish in groups move today, researchers report May 29 in Proceedings of the Royal Society B.

The fossil captures a mass of 259 fish apparently swimming in the same direction. It’s unclear what killed the fish. But a suddenly collapsing sand dune, for example, could have buried them in place in a flash, knocking just a few askew in the process, the researchers suggest.

Analysis of the fish’s positions and orientations suggests they followed the same rules of “attraction” and “repulsion” that govern fish shoals today: The fish are repelled from their nearest neighbors to avoid collisions, but stick with the group by tracking with farther away fishes.

Because collective behavior is seen in so many animals, including the flocking of birds or swarming of insects, scientists believed such behavior evolved long ago. But there has been scant evidence in extinct species, says Nobuaki Mizumoto, a behavioral ecologist at Arizona State University in Tempe.

Mizumoto, whose research usually focuses on how termites build together, stumbled across the fish shoal fossil in a museum in Katsuyama, Japan in 2016. The fossil originally came from sediments in the Green River Formation, a geologic formation spanning what is now Colorado, Wyoming and Utah.

A four-legged whale from Peru indicates that early whales crossed the South Atlantic before 42.6 million years ago and may have propelled like otters: with a robust tail and webbed fingers on their long feet.

Ancient, four-legged whale with otter-like features found along the coast of Peru

April 4, 2019

Cetaceans, the group including whales and dolphins, originated in south Asia more than 50 million years ago from a small, four-legged, hoofed ancestor. Now, researchers reporting the discovery of an ancient four-legged whale — found in 42.6-million-year-old marine sediments along the coast of Peru — have new insight into whales’ evolution and their dispersal to other parts of the world. The findings are reported in the journal Current Biology on April 4.

The presence of small hooves at the tip of the whale’s fingers and toes and its hip and limbs morphology all suggest that this whale could walk on land, according to the researchers. On the other hand, they say, anatomical features of the tail and feet, including long, likely webbed appendages, similar to an otter, indicate that it was a good swimmer too.

“This is the first indisputable record of a quadrupedal whale skeleton for the whole Pacific Ocean, probably the oldest for the Americas, and the most complete outside India and Pakistan”, says Olivier Lambert of the Royal Belgian Institute of Natural Sciences.

Some years ago, study co-author Mario Urbina of Museo de Historia Natural-UNMSM, Peru, discovered a promising area for digging fossils in the coastal desert of southern Peru, named Playa Media Luna. In 2011, an international team, including members from Peru, France, Italy, the Netherlands, and Belgium, organized a field expedition, during which they excavated the remains of an ancient whale they’ve since named Peregocetus pacificus. It means “the traveling whale that reached the Pacific.”

“When digging around the outcropping bones, we quickly realized that this was the skeleton of a quadrupedal whale, with both forelimbs and hind limbs,” Lambert says.

With the help of microfossils, the sediment layers where the skeleton was positioned were precisely dated to the middle Eocene, 42.6 million years ago. Anatomical details of the skeleton allowed them to infer that the animal was capable of maneuvering its large body (up to 4 meters long, tail included), both on land and in the water. For instance, features of the caudal vertebrae (in the tail) are reminiscent of those of beavers and otters, suggesting a significant contribution of the tail during swimming.

The geological age of the new four-limbed whale and its presence along the western coast of South America strongly support the hypothesis that early cetaceans reached the New World across the South Atlantic, from the western coast of Africa to South America, the researchers report. The whales would have been assisted in their travel by westward surface currents and by the fact that, at the time, the distance between the two continents was half what it is today. The researchers suggest that, only after having reached South America, the amphibious whales migrated northward, finally reaching North America.

The international team continues to study the remains of other whales and dolphins from Peru. “We will keep searching in localities with layers as ancient, and even more ancient, than the ones of Playa Media Luna, so older amphibious cetaceans may be discovered in the future,” Lambert says.

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A rare assemblage of sharks and rays from nearshore environments of Eocene Madagascar

This finding, including one new shark species, fills a gap in the known marine record of Madagascar

February 27, 2019

Eocene-aged sediments of Madagascar contain a previously unknown fauna of sharks and rays, according to a study released February 27, 2019 in the open-access journal PLOS ONE by Karen Samonds of Northern Illinois University and colleagues. This newly-described fauna is the first report of sharks and rays of this age in Madagascar.

The Mahajanga basin of northwestern Madagascar yields abundant fossil remains of terrestrial and marine ecosystems, but little is known about fossil sharks and rays during the Eocene Epoch, 55-34 million years ago, in this region. This is in contrast to the numerous shark and ray faunas known from other Eocene sites around the globe, and to shark and ray ecosystems known from older and younger sediments in the Mahajanga basin.

In this study, Samonds and colleagues collected isolated teeth, dental plates, and stingray spines from ancient coastal sediments of the Ampazony and Katsepy regions of the basin, dated to the middle to late Eocene. They identified at least 10 species of sharks and rays, including one new species, Carcharhinus underwoodi. This is the oldest named species of Carcharhinus, a genus that has been globally distributed for the past 35 million years but is known only rarely from the Eocene.